1. Field of the Invention
This invention relates to apparatus for conditioning a fluid, such as cooling or heating an enclosed space in which air is circulated in heat exchange relationship with a refrigerant fluid. More particularly, this invention relates to heat pump apparatus for conditioning an enclosed space and employing a combination of a supplemental fluid assist for low pressure ratio of compression of refrigerant and an optimally designed compressor for improved efficiency.
2. Description of the Prior Art
The prior art is replete with a wide variety of types of apparatuses for air conditioning enclosed spaces such as buildings or the like. Heat pumps have been used to pump heat from one location to another. The heat pumps ordinarily had to compress refrigerant gas from a relatively low suction pressure to a relatively high discharge pressure. This is referred to as a high pressure ratio condition; pressure ratio Pr being defined as (discharge pressure/suction pressure). Even the use of heat pumps augmented by solar energy or the like for the purposes of heating or air conditioning building structures or the like has been known. Use was generally limited to certain geographical areas where the average temperature was relatively high. For example, heat pumps were used in Florida or in the Southwestern United States where the energy from the sun was relatively more plentiful than in other areas of the United States. It has generally been conceded heretofore that in temperature and colder climates the use of the heat pump becomes relatively less efficient. In particular, at temperatures below about 20.degree. F. ambient temperature, the heat pump becomes so inefficient with conventional compressor design as to be of questionable utility.
Merely examining United States patents shows a wide variety of attempts to provide solar assisted heat pump systems for heating. Typical of these prior U.S. patent include U.S. Pat. Nos. 1,101,001; 1,130,870; 1,683,434; 2,559,870; 3,178,113; 3,263,493 and U.S. Pat. No. 4,049,407. There is also an article appearing in the Washington Post on Oct. 12, 1974, entitled "Heat Pump A Key To Solar Heating". These systems have employed various approaches to providing supplemental heat, such as burying the evaporator in the earth and putting heat into the earth about the evaporator, the heat coming from a variety of sources such as solar heat exchangers or the like.
A variety of other approaches has been delineated in patents such as the following U.S. Pat. Nos. 2,829,504; 2,847,190; 2,693,939; 2,689,090; 2,584,573; 2,188,811; 3,189,085; 2,970,817; 4,062,489; 4,065,938; and 4,112,920. In these references, the supplemental sources have been provided for defrosting, and deicing the respective heat exchanger when they have frozen up.
In all of these systems, there has been overlooked one basic disadvantage and that is a combination obtaining a high pressure ratio and the inherent lack of efficiency of conventional compressor design. Expressed otherwise, design was compromised for an arbitrary condition that had a high pressure ratio. In particular, the prior art has not analyzed the requirements for compressor design to take advantage of the theoretical benefits of low pressure ratio that can be effected by high evaporator temperatures and high suction pressure in a system or by low condenser temperatures and low discharge pressure in a system.